1. Field of the Invention
The present invention relates to a lubrication system for the starter of a turbine plant.
Usually, the starter of a turbine plant is integrated into a kinematic chain assembly which is united with the turbine plant and which also comprises a power take-off unit, a transmission shaft, and an accessory control unit from which, in particular, an oil pump, a fuel pump, a hydraulic pump and, in the case of aeronautical applications, various aircraft accessories are driven. When the turbine plant is started, the starter causes rotation of at least one rotary body of the plant through the power take-off unit and the transmission shaft. After starting, the kinematic chain is driven by the plant. The starter is a fragile piece of equipment, particularly if there is a lubrication failure, and damage to it may lead to damage throughout the entire kinematic linkage.
2. Summary of the Prior Art
In order to avoid this happening, various technical solutions have been proposed. Inter alia, disengagement means has been provided between the starter and the transmission line. This solution is illustrated, for example, in U.S. Pat. No. 4,543,074, in EP-A-0059 627, and in FR-A-2 020 349 and FR-A-2 414 146. One of the causes of breakdown due to breakage of the coupling arrangement between the starter and the turbine plant has been traced to lubrication faults which occur in the region of the starter.
One currently used starter lubrication system is shown diagrammatically in FIG. 1 of the accompanying drawings. The principle underlying this system resides in providing the starter with a lubrication system which is totally independent of the lubrication system of the turbine plant. To achieve this, the casing 1 of the starter is provided with an isolated oil bath 1a of limited capacity, and the lubrication is arranged to be of the splash type. The power take-off unit is lubricated by oil from the plant lubrication circuit and forms an independent enclosure 2 comprising an oil bath 2a. Provided between the two enclosures 1 and 2 is a dry interface cavity 3 which is drained at 4. Rotary transmission seals 5 and 6 ensure fluid-tightness between the cavity and each of the two enclosures. However, this arrangement does not provide for any continuous monitoring and if there is any error in filling the starter chamber 1 or any accidental leakage of oil therefrom, the resulting lubrication failure in the starter will give rise to breakages and lead to the serious consequences mentioned earlier.
Another known system involves lubricating the starter by a continuous circulation of oil from the oil supply circuit of the turbine plant. In this system, the oil is returned to the lubrication circuit of the turbine plant, which has the drawback that the oil of the plant becomes polluted by contamination from the starter. A system of this type is illustrated, for example, in GB-A-2144804. A filtering device can be provided, but this makes it necessary to provide for some by-pass in the event of the filter becoming clogged, with the result that it does not fully overcome the risk of the plant oil becoming contaminated or polluted.
The object of the invention is to avoid the disadvantages of the known starter lubrication systems described above, and to provide a system which will guarantee lubrication of the starter while ensuring complete protection of the turbine plant against the risk of its oil lubrication circuit becoming polluted by contamination emanating from the starter.